firmware compatibility between HW2.6 and HW2.7b & 2.6

I saw caution not to upgrade firmware using FW version for differnet HW version.

I have DSO quad HW2.6, can I use firmware for HW2.7b & 2.7?
Sys file version are the same on both firmware for HW2.6 & HW2.7, so I am wondering
if I can use firmware for 2.7 in HW2.6.